Hello fellow Dollars! you may not know me since I don't post really...at all. But I snoop on here pretty often, and by the title, (clearly) I have an issue, otherwise I wouldn't be making this post. I've tried googling solutions and help, but none of it really applies to this specific situation, so I've come for anonymous help.
Lets start at the beginning: A couple years ago, my lifelong best friend had to move to another city due to family issues. Things were tough for a while, but we worked through it and have remained close, we plan to live together in the future. Things got better as he found new friends (some of them questionable, as they didn't quite treat him right) and he could deal with things better. Now, just last year he met this guy, lets call him Tom. He mentioned this guy to me, and I was overjoyed that he *finally* found a good friend! But, slowly, things didn't seem right. First off, my friend had begun to date Tom. I was iffy on this (honestly I was super upset but this isn't about me) but once again, we worked through it. But then Tom began to slowly try cutting me (and my best friends OTHER friends, including the ones that still live by me) out of my best friends life. He logged into my friends social media accounts and blocked me everywhere. This was a red flag to me, but my best friend wasn't concerned yet. I eventually noticed that Tom was very demanding and *ahem* "protective" (looking at all of his messages and snooping through everything). This made me very uncomfortable, and one day Tom flat out messages me insulting me and telling me to just leave my best friends life. Now my best friend was pissed when he heard about this. They argued, my friend apologized to me when Tom refused to. Still, my friend wasn't too concerned. Now we get to the "three month" point in their relationship. Tom does a sudden turnaround and begins to emotional abuse my best friend, which really pisses me off. It started subtle, but slowly got worse in worse- so bad to the point that Tom was constantly threatening suicide, claiming that my best friend "never loved him" and pretty much ignoring any emotional pain my friend was put through, saying "I have it worse so deal with it". Tom was also claiming that my friend was abusing HIM, which wasn't right, since my friend was constantly trying to please him and avoid conflict. Another thing to mention, Tom would always guilt my best friend out of all his paychecks, forcing him to buy him expensive things or else he would throw a public fit and threaten to tell the police that he was being abused.
THIS, THIS was where I finally figured out that my friend was trapped in a toxic relationship. My friend agreed with me, and despite all my pleas for my friend to ditch this asshole, my friend for some reason still saw something in this guy, saying "He didn't used to be like this". Eventually me and my friend found a time to hang out (around the end of summer, right before our final year of highschool-where he and Tom would finally be attending the same school) and my friend FINALLY remembered what it was like to be around a caring person, and that night, he got into a really bad fight with Tom over the phone. I tried talking calm reason into Tom, but in response I recieved the verbal equivalent of a troll's Youtube comment. He also got even more upset that I was hanging out with my friend, and my friend had to lie and say that I was his cousin. Finally, I snapped. Unable to contain my rage at this inconsiderate asshole on the other end of the phone, I went into my friends bathroom and just cried. My friend followed me soon after (I left the door open) apologized to me, and told me he had broken up with Tom.
After this, things were good for the rest of the summer, even if my friend continued to miss Tom (back when he wasn't a dick)
But recently, because they go to the same school now, my friend gave Tom a second chance because Tom kept begging for it and wouldn't leave my friend alone. Things were okay, my friend put his foot down on Tom's behavior and he was listening. But today, my friend sent me a long message explaining that Tom finally had another breakdown right before school. Tom began making a scene because he didn't want to be at schoo, but my friend left because he didn't want to be late to class. Tom lost it at this, began following him all around school, sent threatening messages to my friends phone, and got into my friends locker and threw EVERYTHING away, all his homework and notes (My friend sent a picture of the messages Tom was sending, and Tom even sent a picture of himself trashing everything) My friend was very upset when he when into the hall and found Tom doing this, and Tom just laughed.
And then the abuse escalated to physical, because my friend told me that Tom pushed him down the stairs and kept shoving him into lockers. He even sent me the picture of the giant bruises he got from the stairs. Tom then threatened that, if my friend told anyone about this, then he was going to claim that my friend sexually assaulted him. Which, they have never had sex, mostly because I convinced my friend that it was a really bad idea
My friend is really upset, and I am too, I'm now worried about his physical safety. In good news, my friend turns 18 in half a year and has plans to move back to my city as soon as he does. However, I have no idea how to get help for my friend or what to do. He goes to the same school as Tom, Tom has made it a point to know all his passwords and his locker combination. My friend is still reluctant to call the police or anything.

So now that I have told the story: what should I do? Do I just wait until my friend moves back here, and help him through it until then? Or how do I convince my friend that he should take legal action (like a restraining order)? I can't bring myself to call the police, I don't want my friend to lose trust in me when I already feel bad for asking for help here. My friend means everything to me, unlike Tom, I genuinely love and care about him (even if he doesn't realize it until he's standing next to me). I don't want to risk him getting mad at me, if theres legal action, I want it to be consentual.

Sorry for such a long post, please help me, I can't stand seeing my best friend tortured anymore. Oh, and his family won't help at all, they just want him out of the house as soon as possible.

These scenarios typically have a few options.

1. Confront them logically with clear communication. (seemingly out of the question)
2. (you or your friend) exclude yourself from the situation all together. Say you're done and just be done.
3. Handle it legally. Pretty self explanatory. It's the "right way" to avoid escalating it directly, and anything from that point on can be used as firepower.
4. Beat the snot out of them and risk being taken to court yourself.

I'm not strongly advising for or against any of these options. Shitty people simply aren't worth your time in most cases so I'd do my best to just back out.